Wireless communication systems generally include a plurality of communication devices, such as mobile or portable radio devices that are located in multiple sites. Each site may include a set of base stations or repeaters for communicating information such as voice, data, control, and network management traffic between the communication devices and with each other. Such mobile or portable radio devices often need an explicit acknowledgment in order to know the success or failure of a data delivery. Many cellular systems include random access procedures that dictate an explicit acknowledgment as an individual message to the subscriber radio that initiated the request. Since the dominant service in cellular systems is telephony, the number of resources for user services becomes the capacity bottle neck as compared to control channel transactions. For dedicated land mobile radio (LMR) system, where the most dominant service is Push-to-Talk (PTT), the control channel on which the calls are being set up becomes a bottle neck.
Some LMR systems, such as Terrestrial Trunked Radio (TETRA) systems were based on cellular principles and accordingly their random access procedures are similar to cellular networks incorporating explicit acknowledgments. In order to handle the potential overload of the control channel, the TETRA standard suggests extending control channel capacity by adding secondary control channels. This method, however, results in increased utilization of resources for control rather than for user services, which is unacceptable in cases where the number of available physical resources is limited. In some systems, explicit acknowledgments are needed for both control channel transactions and data messages. In systems that incorporate slotted data architecture, the channel sends explicit acknowledgment to a subscriber for every scheduled data slot. Explicit acknowledgment requires a full outbound slot in order to contain the identifier of the subscriber radio requiring the acknowledgment as well as the actual acknowledgment information indicating the success or failure of the data delivery. This explicit acknowledgment consumes 17%-30% of outbound bandwidth depending on the data packet size, resulting in total bandwidth utilization ranging from 55% for packets with ten (10) scheduled data slots to 80% for packets with two (2) scheduled data slots.
Accordingly, there is a need for a solution that improves slotted data channel outbound efficiency.
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